1. Field of the Invention
This invention relates to a meter module that facilitates electric wiring and mounting of electric instruments at the dashboard portion of an automobile.
2. Description of the Prior Art
FIG. 33 shows a conventional wired state of wiring harnesses. A deal of electric equipment is disposed around the dashboard 2 of a vehicle body 1. Therefore, control circuit units 4A", 4B". . . that control the equipment, meters 51, indicator lamps and switches 45 are also gathered. Consequently, the number of wires that constitute a dashboard wiring harness becomes enormous, making the harnesses enlarged and heavy and causing the wired state of the harnesses complicated, resulting in much labor and time required in installation. The maintenance is also made difficult.
Designated 74A is a cowl side wiring harness, 74B an engine room main wiring harness, 74C, 74C floor wiring harnesses, 74D', 74D' door wiring harnesses, and 75A, 75B . . . connections by connectors and the like.
To ease such a situation, it is proposed in Japanese Patent Publication Specification No. Sho 57-38457 that to simplify the wired state of wiring harnesses and prevent their enlargedness, a plurality of electric juntion boxes--which gather therein branch connectons of wiring harnesses and carry a number of circuit-protecting fuses and control relays--are dispersedly arranged at suitable places in an automobile.
FIG. 34 is a wiring diagram of a tail lamp system with such electric junction boxes used. Designated 57A, 57B are tail lamps, 58A, 58B clearance lamps, and 1A an engine room with an engine 59 and a battery (not shown) therein. In the region 1B near the dashboard an instrument panel 100 with a tail lamp alarm lamp 52, a tail relay 55, an electric junction box 101 with a main fuse 56A, a tail fuse 56B and a meter fuse 56C, a lamp disconnection detection relay 102 and a tail switch 45 are arranged.
When the tail switch 48 is put on, the contacts of the tail relay 55 are closed and the current flows through the circuit with the tail fuse 56B to light the lamps 57A, 57B, 58A and 58B. When either one of the lamps 57A and 57B is disconnected, the lamp disconnection detection relay 102 operates and the alarm lamp 52 inside the instrument panel 100 is lighted.
FIG. 35 is a block diagram of the wiring around such electric junction box 101, lamp disconnection detection relay 102 and instrument panel (combination meter) 100 combined with control circuit units 55 such as a speed control relay and integration relay.
Inside the instrument panel 100 a number of meters 51 such as an oil meter, battery meter, speed meter and tachometer, their movements 29 and lamps 52 such as an indicator lamp, alarm lamp and lighting lamp are implemented. The speed meter 51A and the tachometer 51B are respectively provided with control circuits 103A and 103B for their exclusive use. Further, the above-mentioned Control circuit units 55 are also dispersedly arranged. Thus, the power lines and signal lines that connect these are very large in number, and the complicatedness is not still solved by limitingly arranging a small number of electric junction boxes 101.
Under these conditions, it is proposed in Japanese Patent Application Laid-Open Specification No. Hei 2-45238 that to reduce the number of circuits inside an electric junction box and the number of their connecting wires and simplify the wiring harnesses around the dashboard, the internal circuit of an instrument panel include a branch circuit with joints for connection with a wiring harness and the instrument panel take over a part of branch connections of the wiring harness.
Further, in Japanese Patent Application Laid-Open Specification No. Hei 4-266537 a circuit structure is proposed which comprises, as shown in FIG. 36, switches/instruments (not shown) implemented in a cluster 105 at a dashboard portion 104, a flexible printed circuit board 106 glued to the rear surfac of the cluster for forming electric circuits for the switches/instruments, and electronic control substarates 109A-109F dispersedly arranged at terminals of the circuit board 106 with electronic function parts 108 mounted thereon for the memory, operation and the like needed for the electronic control of the switches/instruments.
It is to be noted, however, that if the internal circuit of the instrument panel takes over part of branch circuits of a wiring harness or of an electric junction box, insofar as control circuit units for electric equipment are dispersedly arranged, there is a limit to simplifying the wiring harnesses, making it difficult to cope with the accelerative electronization foreseen in view of the pursuit of safety and comfortableness.
Further, although directly arranging the electric circuits (flexible printed circuit board) for the switches/instruments and the electronic control substrates on the cluster rear surface is advantageous in that control circuit units are gathered on the cluster rear surface, it involves the following disadvantages: It is technically difficult to adapt to the irregularities on the rear surface. Further, for each type and grade of a vehicle and for each partial change in the specification, the design and production must be changed, resulting in an increase in cost due to multikind and small-quantity production.